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Does any one have any experience using multiple subs in a two channel or home theater system? If so, what did you like and not like?

Much depends on how you configure the multiple subs. What I like about multi-sub set-ups is better consistency from seat to seat, smoother low frequency response, greater overall dynamics. A couple of reason for that last part: multiple subs means that each sub is taxing its amp less, leaving more headroom for instantaneous peaks; and, by freeing the main speakers (and their amps) from having to reproduce low frequencies, they have more headroom as well.

Of course the thing I like most is that you can place your subs at the locations that give you best bass response in your room AND place your speakers where they give you best soundstage and imaging. No need to compromise one for the other. This applies to any sort of speaker layout: mono, stereo, surround.

Quote:

Originally Posted by Talk2Me

Also if any diff. between e.g., 2 JL subs vs. 1 JL sub with 2 drivers.

I would opt for the former, since there are advantages to spreading a pair of subwoofers away from each other in the room; can't do that with the latter (unless you're handy with a saw).

Typical small room acoustics benefits significantly from a multiple sub/multiple location subwoofer system approach. By far the two most important elements in audio are the loudspeakers, and their interaction and optimization in the room. Utilizing two subs, one can opt for a selective mode cancellation approach, to minimize modal issues in whatever room axis needed. If the biggest problems exist in the front to back direction, then employing a sub front and rear will pay dividends. Likewise, if the issue is with lateral modes across the width of your room, then spacing them left and right of a median line will yield you the best results.

Ideally, employing four subs can address both axis, and this is illustrated in the AES paper below.

You may enjoy reading this AES paper by Welti and DeVantier,....it's very good and illustrates the benefits of a multiple sub approach.

All the benefits listed before are true. Better bass over a larger area. More output, lower distortion, less compression, thus dynamic portrayal is rendered much more accurately. All said, the biggest benefit is reduction of modal issues, Thus, better delineation of the subwoofer range can be expected if properly optimized wrt time/freq EQ'ing.

You should always use two subwoofers in any system. Using only one subwoofer makes the bass disembodied from the midrange and mid-bass. In order to get sufficient cone area to properly push enough air to get a smooth sound, you need two subwoofers.

You should always use two subwoofers in any system. Using only one subwoofer makes the bass disembodied from the midrange and mid-bass. In order to get sufficient cone area to properly push enough air to get a smooth sound, you need two subwoofers.

You should always use two subwoofers in any system. Using only one subwoofer makes the bass disembodied from the midrange and mid-bass. In order to get sufficient cone area to properly push enough air to get a smooth sound, you need two subwoofers.

I disagree with this statement. One sub integrates perfectly with my system.

No, but my equipment was setup by cedia approved persons, and the room also was acoustically treated by professionals. I am also using the McIntosh MX150 with room perfect. There really is no place in my room for a second sub. You can see my room from my utube video calkid1234

Essentially like having a single sub, since you can only place it in one location. The reason multiple subs can make such an improvement over a single sub is because you get to take advantage of multiple locations in the room.

Essentially like having a single sub, since you can only place it in one location. The reason multiple subs can make such an improvement over a single sub is because you get to take advantage of multiple locations in the room.

Low frequencies are non-directional, which is what allows subwoofer/satellite combos to work. A single subwoofer will result in peaks and dips in the frequency response. One of the most effective ways to bring down the peaks and fill in the dips is to use additional subs, typically placed well away from each other. You can also try to EQ the peaks and (to a lesser extent) the dips to smooth them out, but that will only be effective for a small listening area. Multiple subs can be arranged to yield similar results in several seats, which then allows the EQ to be effective over a much larger listening area. Check out the paper that FOH linked to.

Low frequencies are non-directional, which is what allows subwoofer/satellite combos to work. A single subwoofer will result in peaks and dips in the frequency response. One of the most effective ways to bring down the peaks and fill in the dips is to use additional subs, typically placed well away from each other. You can also try to EQ the peaks and (to a lesser extent) the dips to smooth them out, but that will only be effective for a small listening area. Multiple subs can be arranged to yield similar results in several seats, which then allows the EQ to be effective over a much larger listening area. Check out the paper that FOH linked to.

Thanks, just asking, as my speakers do not need subs, but it is good to know.

I disagree with this statement. One sub integrates perfectly with my system.

Quote:

Originally Posted by Talk2Me

I thought subwoofers are mono directional?

Quote:

Originally Posted by sdurani

Low frequencies are non-directional, which is what allows subwoofer/satellite combos to work. A single subwoofer will result in peaks and dips in the frequency response.

Let's throw one more cat into the bag. Low frequencies are multi-directional, which means they radiate in a 360 degree pattern more readily and completely than other frequencies, and are thus less able to be localized because they have less directivity. What they do have a lot of as Sanjay points out are peaks and valleys around the room when only one radiator is in the room. A group of CEDIA geniuses, room treatments, and wizardly electronics can overcome most of this for the best seat in the house, but at the expense of every other location.

As Sanjay and I discovered through brute force of moving subs around (and then increasing the number from two to four), two well-placed or four well-placed subs in even a difficult room can do more to improve and even out LF response than a dedicated bass management system with calibration mics whose sole job is to integrate the LF into the whole system. We validated the Harman/JBL white paper through actual implementation and decided they really did know what they were writing about.

So while Turbo Ron's free to disagree, and no doubt his single sub works well with the effort put into integrating it in a great system, I can't imagine it's "perfectly" integrated. The science and my own experience of allowing a single sub to be replaced by two (or even four) subs just doesn't back that up.

Let's throw one more cat into the bag. Low frequencies are multi-directional, which means they radiate in a 360 degree pattern more readily and completely than other frequencies, and are thus less able to be localized because they have less directivity. What they do have a lot of as Sanjay points out are peaks and valleys around the room when only one radiator is in the room. A group of CEDIA geniuses, room treatments, and wizardly electronics can overcome most of this for the best seat in the house, but at the expense of every other location.

As Sanjay and I discovered through brute force of moving subs around (and then increasing the number from two to four), two well-placed or four well-placed subs in even a difficult room can do more to improve and even out LF response than a dedicated bass management system with calibration mics whose sole job is to integrate the LF into the whole system. We validated the Harman/JBL white paper through actual implementation and decided they really did know what they were writing about.

So while Turbo Ron's free to disagree, and no doubt his single sub works well with the effort put into integrating it in a great system, I can't imagine it's "perfectly" integrated. The science and my own experience of allowing a single sub to be replaced by two (or even four) subs just doesn't back that up.

What he said. I recently replaced a REL Studio 3 with 3 subs, that had their crossovers tweaked and equalized by an expert, Mark Seaton. The results were astounding. The bass response was equalized through the whole room, with no peaks or valleys. The room is now relatively flat to 10 hz., without room correction, but with judicious placement of speakers and room treatments. And this is a difficult room.

What he said. I recently replaced a REL Studio 3 with 3 subs, that had their crossovers tweaked and equalized by an expert, Mark Seaton. The results were astounding. The bass response was equalized through the whole room, with no peaks or valleys. The room is now relatively flat to 10 hz., without room correction, but with judicious placement of speakers and room treatments. And this is a difficult room.

David

Flat to 10 hz?! Very impressive indeed. So, I take it, you listen to soundtracks and organ music? . What makes your room difficult? Is it a teenager? Sorry, could not help it. Seriously, how do you determine how many subs do you need?

Essentially like having a single sub, since you can only place it in one location. The reason multiple subs can make such an improvement over a single sub is because you get to take advantage of multiple locations in the room

Hi Sanjay ... how'd you like your visit to the "farm"?

Multiple subs (all set to the same phase) in a room behave approximately as would a single sub positioned at the acoustic mid-point between all the subs. What you then get is the ability (among those advantages in the Welti paper) is the ability to then individual calibrate each sub to reduce the depth (if not eliminate) of modal nulls in the seating locations. Peaks can then be addressed in the same manner or with PEQ. Let's assume in your set up process you discover the best bass response (in the seating location(s)) is when the sub is somewhere out in the middle of the floor. You could then position two subs such that your "ideal" location is 1/2 between the two physical subs to achieve the same result.

Using individualy subs (rather than full range speakers), you also have the advantage of getting the subs close enough to the walls to avoid SBIR notches and the mains far enough to avoid SBIR notches.

That is not to say you cannot get satisfying results with a single sub or with a full range system. It is a different challenge and often extremely difficult to get smooth bass response over a larger seating area.

Flat to 10 hz?! Very impressive indeed. So, I take it, you listen to soundtracks and organ music? . What makes your room difficult? Is it a teenager? Sorry, could not help it. Seriously, how do you determine how many subs do you need?

I currently have three teenage daughters, so a very rigid room with brick walls is nothing. Except if you are a home theater. I don't listen to anything that low. But, when the dragons roared in "How to Train a Dragon", my shirt collar actually moved from the force of the bass. There is an earlier thread detalling his work, but it is a help when you have a subwoofer designer and manufacturer calibrate his subs to the room. As to the number of subs, I would have gone to four if Mark thought that it was necessary.

You should always use two subwoofers in any system. Using only one subwoofer makes the bass disembodied from the midrange and mid-bass. In order to get sufficient cone area to properly push enough air to get a smooth sound, you need two subwoofers.

Thanks, just asking, as my speakers do not need subs, but it is good to know.

If I had a dollar for everytime I've heard that statement! I thought the same way at one time! What speakers are you using and how large is your room? My room is approx 2100 sq/ft. Try testing your speakers at about 90-95 db and tell me what you hear from your speakers? How loud do you play them in your room? I got curious one day and I took my trusty bass setup test disc (Bass Mechanix) and decided to run the low frequency sweep with my Wilson Watt Puppy 7's. It sounded pretty darn good until around 40hz.There was bass still being produced at that frequency but I could hear/feel the frequencies below 40hz start to roll off. Although even though the speaker tried it could not reproduce the note realistically at the lower levels. Fast forward to the addition of two JL Audio F113's and ran the test again. The same band of frequencies were reproduced easily all the way down to 15hz. The rooms walls were definitely moving on that test. YMMV of course.

If I had a dollar for everytime I've heard that statement! I thought the same way at one time! What speakers are you using and how large is your room? My room is approx 2100 sq/ft. Try testing your speakers at about 90-95 db and tell me what you hear from your speakers? How loud do you play them in your room? I got curious one day and I took my trusty bass setup test disc (Bass Mechanix) and decided to run the low frequency sweep with my Wilson Watt Puppy 7's. It sounded pretty darn good until around 40hz.There was bass still being produced at that frequency but I could hear/feel the frequencies below 40hz start to roll off. Although even though the speaker tried it could not reproduce the note realistically at the lower levels. Fast forward to the addition of two JL Audio F113's and ran the test again. The same band of frequencies were reproduced easily all the way down to 15hz. The rooms walls were definitely moving on that test. YMMV of course.

I use Mcintosh XR200s which sound to my ear to have more bass than my previous LS360. I can't measure the XR200s right now at full power because of my current living arrangements. However, the LS360 measured up 3db at 20hz at, are you ready?, 115db. There are exceptions. Most speakers are not full range, but some are, Mcintosh in particular. One of the reasons, I have never purchased Wilsons is that you really need a sub with most of the models and the speakers are already premium priced. If I am going to pay 20k, the retail of my speakers, I want real full range. The room measured 24.5 by 17 by 9. Is your room really 2100 square feet? That would make it like 40 feet by 52 feet?

Don't get me wrong the Wilson's reproduced it just not to my level of satisfaction. Let's try to stay away from the Wilson bashing. I have a dealer friend who sells Mc Intosh gear. Never heard the speakers, just the amps which I did like!

Don't get me wrong the Wilson's reproduced it just not to my level of satisfaction. Let's try to stay away from the Wilson bashing. I have a dealer friend who sells Mc Intosh gear. Never heard the speakers, just the amps which I did like!

It's not any single brand. A lot of high-end speakers ate designed that way. My suspicion is that room correction is going to change that eventually.

Stunning! Having never been in an Erskine-designed room and having never heard a system tuned by Jim (despite knowing him since before he was a calibrator), I was expecting it to sound good with movies, but I was shocked at how nice it sounded with music. Most home theatres are overly dampened for my personal tastes, with too little of the spaciousness I crave with music. Not this time: song after song I heard a wide, lush soundstage, rich in detail and imaging. Even Chuck noticed stable imaging well outside the L/R speakers. The other treat that day was meeting Joe; what a truly nice guy.

Multiple subs (all set to the same phase) in a room behave approximately as would a single sub positioned at the acoustic mid-point between all the subs. What you then get is the ability (among those advantages in the Welti paper) is the ability to then individual calibrate each sub to reduce the depth (if not eliminate) of modal nulls in the seating locations. Peaks can then be addressed in the same manner or with PEQ. Let's assume in your set up process you discover the best bass response (in the seating location(s)) is when the sub is somewhere out in the middle of the floor. You could then position two subs such that your "ideal" location is 1/2 between the two physical subs to achieve the same result.
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Dennis (or anyone that knows the answers)-
I have some follow-up questions. I know that multiple subs set-up ala Welti will act as a single sub at some mid point between the subs. My question is does that assume that they are playing at the same volume level? And I guess my follow-up is if the subs are different types (and sizes) and you have adjusted using different volumes (more like Earl Geddes method or the sub management process (SFM) by Harmon) are you still getting a "virtural sub" somewhere in 3 dimensional space? If so, and you do that before equalization, is it like equalizing a single virtual sub?

Identical subs at the same SPL and Phase act approximately as would a single sub at the mid-point between the subs. Let's assume you have two subs. If you raise the SPL on one of the subs, that would move the "mid-point" away from the louder of the two subs. Same is true with 4 to 500 subwoofers.

Matched identically is always the starting point in the calibration process. You can then measure the response at each seating location and develop your EQ strategy from that point forward.